Buckingham Palace has issued a fresh denial of allegations an American woman kept as an underaged "sex slave" by a Wall Street billionaire was forced to have sexual relations with Britain's Prince Andrew.

The woman, identified in legal documents only as "Jane Doe #3," has alleged in a US court filing that she had been kept as a "sex slave" by financier Jeffrey Epstein, a friend of the prince.

Andrew, the Duke of York, and prominent US attorney Alan Dershowitz, one of Epstein's defence lawyers, have both vigorously denied the allegations.

In a strongly-worded response on Friday, Buckingham Palace said that "any suggestion of impropriety with underage minors is categorically untrue".

But the palace took the even more unusual step of issuing a second statement after British Sunday newspapers printed details of interviews the plaintiff has given in recent years.

"It is emphatically denied that the Duke of York had any form of sexual contact or relationship" with the woman, the palace said.

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The Mail on Sunday and the Sunday Mirror newspapers both published details of interviews given by the woman in recent years, in which she discusses three alleged encounters with Andrew.

Meanwhile, the Sunday Express reported that the prince was due to fly back into Britain after taking a ski trip to Switzerland. A royal source confirmed Andrew had been away on a private holiday abroad.

Following the denials from the prince and Dershowitz, "Jane Doe #3" told The Guardian newspaper that she refuses to be "unjustly victimised again".

According to the motion filed in a Florida court this week, the woman alleges she was "forced to have sexual relations" with 54-year-old Andrew in London, New York and the Caribbean at Epstein's behest.

Epstein, a known friend of Queen Elizabeth II's second son, was convicted in 2008 of soliciting an underage girl for prostitution and served a prison term.

The woman claimed she was his sex slave from 1999 through to 2002.

In a statement to The Guardian she said: "These types of aggressive attacks on me are exactly the reason why sexual abuse victims typically remain silent and the reason why I did for a long time.

"That trend should change. I'm not going to be bullied back into silence."

Andrew is fifth in line to the British throne and was the first child born to a reigning British monarch in more than a century. He remains close to his ex-wife Sarah, with whom he has two daughters, Princesses Beatrice and Eugenie.

The naval officer, who flew helicopters in the 1982 Falklands War, was Britain's special representative for international trade and investment for 10 years until 2011.

The prince gave up the business ambassador post following the intense scrutiny he faced over his relationships with Epstein, candid comments recorded in US diplomatic cables exposed by WikiLeaks and links with key figures in repressive regimes.

Dershowitz, whom "Jane Doe #3" was allegedly forced to have sex with on several occasions, told AFP the story was "made up".

He accused the woman of "filing a false and malicious legal proceeding" in an attempt to extort money from his former client.

In a BBC radio interview, the Harvard Law School professor urged Andrew to fight back hard against the allegations.

"If she's lied about me, which I know to an absolute certainty she has, she should not be believed about anyone else," Dershowitz said.

"You have to fight back with every resource and ounce of energy available to you.

"I will swear under oath -- and I challenge them to swear under oath -- that it did not happen," he added.

The filing in which Andrew is named is to be included in an ongoing civil case that accuses federal prosecutors of cutting a plea-bargain deal with Epstein without consulting his victims, in violation of the US Crime Victims Rights' Act.